Vinyl siding currently has a 48 percent share of the U.S. siding market outpacing wood, stucco, stone, concrete, brick and metal. The vinyl siding market is expected to grow by an additional two percent by the year 2005. This explosive growth is the result of vinyl's outstanding durability and its versatility in terms of color, texture and patterns. Currently, many manufacturers of vinyl siding are having difficulty keeping up with market demand. The ability to extrude the polyvinyl chloride into the finished vinyl siding product is principally limited by the feed rate capacity of the production lines. For example, many vinyl siding components are profile extruded which requires extruding polyvinyl chloride through a die at a haul-off rate of between six and ten feet per minute. This compares with feed rates in excess of 150 feet per minute for some post-form extruded products. The dual undersill component had been profile extruded at a haul-off rate of approximately 3 meters per minute (10 feet per minute). A continuous loop version of the dual undersill which will be discussed in more detail below can now be post-form extruded at a haul off rate of approximately 18 meters per minute (60 feet per minute).
The principal drawback to the post-form extrusion process, at least until application of the present methodology, was its inability produce a product, such as the dual undersill, with a complex continuous loop configuration wherein a single sheet of polyvinyl chloride is bent or formed into the desired geometry by pressing it through one or more fixtures at a high rate of speed.
Profile-extrusion of polyvinyl chloride components is a common industrial practice across the globe. Numerous common items are produced from extruded polyvinyl chloride including, guttering, window frames and vinyl siding components. During the production process, the polyvinyl chloride resin is heated in an extrusion device and fed into a profile fixture where the desired shape is forced out of a die under considerable pressure. The process produces precisely dimensioned components, however, one major drawback to the process is the rate of production. It is common to experience a profile-extrusion process rate of no greater than 1.8 to 3 meters per minute (6 to 10 feet per minute). Profile-extrusion of polyvinyl chloride components is a relatively slow process and in the vinyl siding production business, companies must maintain high rates of production to remain profitable.
A second process for producing components manufactured from polyvinyl chloride is post-form extrusion. It is possible, utilizing post-form extrusion, to run production lines at speeds in excess of 45 meters per minute (150 feet per minute), or more than 10 times the speed of profile-extrusion production lines. With post-form extrusion, the extruded and heated polyvinyl chloride is formed into a flat sheet, embossed with a pattern or grain structure for aesthetic appeal, then depending upon the complexity of the desired finished product the sheet is first fed into a preform stage or directly into a fixture, also known as a calibrator, to achieve the desired profile and dimensions. Conventional wisdom has been that components with complex geometries, especially those that are characterized as having a continuous loop construction, wherein a first layer of the component is positioned in the fixture and then a second layer is wrapped back around in a continuous loop immediately atop the first layer could not be produced utilizing post-form extrusion if production rates were in excess of 3 meters per minute (10 feet per minute). Producing continuous loop components such as dual undersill trim having even a few critical bends has proven difficult for many siding manufacturers.
A vinyl siding component, referred to as dual undersill trim, is utilized to facilitate the installation of vinyl siding that is adjacent to a soffit. This is a commonly utilized component produced by many vinyl siding manufacturers, however, it is currently universally produced using the profile-extrusion process because it possesses a geometry considered too challenging to produce using post-form extrusion techniques if speeds much in excess of those utilized in profile-extrusion are sought. Numerous vinyl siding manufacturers have previously attempted to produce dual undersill trim utilizing post-form extrusion, however, the challenges of producing the component utilizing a continuous loop process at speeds approaching 18 meters per minute (60 feet per minute) have proven insurmountable up until now.
The function of dual undersill trim, as opposed to single undersill trim, is to minimize the deformation of the siding in proximity to the soffit or window sill, by providing the siding installer with two positions for placement of the cut edge of the top course of the siding within the dual undersill component. Minimizing deformation is particularly important for maintaining the aesthetic appeal of the siding in proximity to the soffit. Deformation of the siding will manifest itself in an uneven or bulging surface near the soffit. The dual undersill trim allows a siding installer to select between two positions for receiving, as well as obscuring, the cut edge of the siding. The entry point of the first slot of the dual undersill is in close proximity to the vertical wall that the siding is covering and the second slot is spaced away from the wall by approximately 8 mm (0.31 inches) or roughly the span of the center rib typically found on most vinyl siding.
During installation, when the top course of the vinyl siding is cut in proximity to the soffit such that the horizontally cut edge is closer to the plane perpendicular to the back edge of the center rib of the siding than with the front edge of the center rib, then the terminating edge of the vinyl siding is most easily inserted into the dual undersill position closest to the wall being sided. If, however, the cut edge of the siding is closer to the plane perpendicular to the front edge of the center rib than the vertical plane of the back edge of the center rib, then the cut edge should be inserted into the dual undersill position located furthest from the wall being sided with vinyl.
A need in the art therefore exists for a method of producing thermoplastic components of complex geometry at a high rate of speed without causing jamming of the production fixtures or sacrificing the dimensional requirements of the product. A further need exists for an undersill component that offers the vinyl siding installer the option of placing the cut edge of the top course of the vinyl siding in one of two positions within the undersill trim. The two placement options minimize the deformation experienced by the siding as it is installed adjacent the soffit, or beneath the sill of a window frame.